/**
 * Created with IntelliJ IDEA.
 * Description:单链表
 * User: 晓星航
 * Date: 2022-11-01
 * Time: 15:35
 */
class ListNode{
    public int val;
    public ListNode next;//ListNode 储存的是节点类型

    public ListNode(int val) {
        this.val = val;
    }
}

public class MyLinkedList {
    public ListNode head;

    public void creatList() {
        ListNode listNode1 = new ListNode(12);
        ListNode listNode2 = new ListNode(23);
        ListNode listNode3 = new ListNode(34);
        ListNode listNode4 = new ListNode(45);
        ListNode listNode5 = new ListNode(56);
        listNode1.next = listNode2;
        listNode2.next = listNode3;
        listNode3.next = listNode4;
        listNode4.next = listNode5;
        this.head = listNode1;
    }
    //打印链表中的所有元素
    public void display() {
        ListNode cur = this.head;
        while (cur != null) {
            System.out.print(cur.val + " ");
            cur = cur.next;
        }
        System.out.println();
    }
    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key) {
        ListNode cur = this.head;
        while(cur != null){
            if (cur.val == key) {
                return true;
            }
            cur = cur.next;
        }
        return false;
    }
    //得到单链表的长度
    public int size(){
        ListNode cur = this.head;
        int count = 0;
        while (cur != null) {
            count++;
            cur = cur.next;
        }
        return count;
    }
    //头插法
    public void addFirst(int data) {
        ListNode node = new ListNode(data);
        node.next = this.head;
        this.head = node;
    }
    //尾插法
    public void addLast(int data) {
        ListNode node = new ListNode(data);
        if (this.head == null) {
            this.head = node;
        } else {
            ListNode cur = this.head;
            while (cur.next != null) {
                cur = cur.next;
            }
            cur.next = node;
        }
    }

    /**
     * 找到index - 1位置的结点
     * @param index
     * @return
     */
    public ListNode findIndex(int index) {
        ListNode cur = this.head;
        while(index != 0) {
            cur = cur.next;
            index--;
        }
        return cur;
    }
    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int data) {
        if(index < 0 || index > size()) {
            System.out.println("size 位置不合法");
            return;
        }
        if(index == 0) {
            addFirst(data);
            return;
        }
        if(index == size()) {
            addLast(data);
            return;
        }
        ListNode cur = findIndex(index);
        ListNode node = new ListNode(data);
        node.next = cur.next;
        cur.next = node;
    }
    //删除第一次出现关键字为key的节点
    /**
     * 找到要删除关键字 key的节点
     * @param key
     * @return
     */
    public ListNode searchPerv(int key) {
        ListNode cur = this.head;
        while(cur.next != null) {
            if(cur.next.val == key) {
                return cur;
            }
            cur = cur.next;
        }
        return null;
    }
    public void remove(int key) {
        if(this.head == null) {
            System.out.println("单链表为空");
            return;
        }
        if(this.head.val == key) {
            this.head = this.head.next;
            return;
        }
        ListNode cur = searchPerv(key);
        if(cur == null) {
            System.out.println("没有要删除的节点");
            return;
        }
        ListNode del = cur.next;
        cur.next = del.next;
    }
    //删除所有值为key的节点
    public ListNode removeAllKey(int key) {
        if(this.head == null) {
            return null;
        }
        ListNode prev = this.head;
        ListNode cur = this.head.next;
        while(cur != null) {
            if(cur.val == key) {
                prev.next = cur.next;
                cur = cur.next;
            } else {
                prev = cur;
                cur = cur.next;
            }
        }
        //最后处理头
        if(this.head.val == key) {
            this.head = this.head.next;
        }
        return this.head;
    }
    //清除链表中所有元素
    public void clear() {
        while (this.head != null) {
            ListNode curNext = this.head.next;
            this.head.next = null;
            this.head = curNext;
        }
    }
    //按照x和链表中元素的大小来分割链表中的元素
    public ListNode partition(int x) {
        ListNode bs = null;
        ListNode be = null;
        ListNode as = null;
        ListNode ae = null;
        ListNode cur = head;
        while (cur != null) {
            if(cur.val < x){
                //1、第一次
                if (bs == null) {
                    bs = cur;
                    be = cur;
                } else {
                    //2、不是第一次
                    be.next = cur;
                    be = be.next;
                }
            } else {
                //1、第一次
                if (as == null) {
                    as = cur;
                    as = cur;
                } else {
                    //2、不是第一次
                    ae.next = cur;
                    ae = ae.next;
                }
            }
            cur = cur.next;
        }
        //预防第1个段为空
        if (bs == null) {
            return as;
        }
        be.next = as;
        //预防第2个段当中的数据，最后一个节点不是空的。
        if (as != null) {
            ae.next = null;
        }
        return be;
    }
    public ListNode deleteDuplication() {
        ListNode cur = head;
        ListNode newHead = new ListNode(-1);
        ListNode tmp = newHead;
        while(cur != null) {
            if (cur.next != null && cur.val == cur.next.val) {
                while (cur.next != null && cur.val == cur.next.val) {
                    cur = cur.next;
                }
                cur = cur.next;
            } else {
                tmp.next = cur;
                tmp = tmp.next;
                cur = cur.next;
            }
        }
        //防止最后一个结点也是重复的
        tmp.next = null;
        return newHead.next;
    }
    public boolean chkPalindrome(ListNode head) {
        if (head == null) {
            return true;
        }
        ListNode fast = head;
        ListNode slow = head;
        while (fast != null && fast.next != null) {
            fast = fast.next.next;
            slow = slow.next;
        }
        //slow走到了中间位置
        ListNode cur = slow.next;
        while (cur != null) {
            ListNode curNext = cur.next;
            cur.next = slow;
            slow = cur;
            cur = curNext;
        }
        //反转完成
        while (head != slow) {
            if(head.val != slow.val) {
                return false;
            } else {
                if (head.next == slow) {
                    return true;
                }
                head = head.next;
                slow = slow.next;
            }
            return true;
        }
        return true;
    }
//    public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
//        if (headA == null || headB == null) {
//            return null;
//        }
//        ListNode pl = headA;
//        ListNode ps = headB;
//        int lenA = 0;
//        int lenB = 0;
//        while (pl != null) {
//            lenA++;
//            pl = pl.next;
//        }
//        pl = headA;
//        while (ps != null) {
//            lenB++;
//            ps = ps.next;
//        }
//        ps = headB;
//        int len = lenA - lenB;//差值步
//        if (len < 0) {
//            pl = headB;
//            ps = headA;
//            len = lenB - lenA;
//        }
//        //1、pl永远指向了最长的链表，ps永远指向了最短的链表   2、求到了插值len步
//        //pl走差值len步
//        while (len != 0) {
//            pl = pl.next;
//            len--;
//        }
//        //同时走直到相遇
//        while (pl != ps) {
//            pl = pl.next;
//            ps = ps.next;
//        }
//        return pl;
//    }
    public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
        if (headA == null || headB == null) {
            return null;
        }
        ListNode pl = headA;
        ListNode ps = headB;
        int lenA = 0;
        int lenB = 0;
        while (pl != null) {
            lenA++;
            pl = pl.next;
        }
        pl = headA;
        while (ps != null) {
            lenB++;
            ps = ps.next;
        }
        ps = headB;
        //求pl和ps的差值
        int len = lenA - lenB;
        if (len < 0) {
            pl = headB;
            ps = headA;
            len = lenB - lenA;
        }
        while (len != 0) {
            pl = pl.next;
            len--;
        }
        while (pl != ps) {
            pl = pl.next;
            ps = ps.next;
        }
        return pl;
    }
    public  static  ListNode mergeTwoLists(ListNode headA,ListNode headB) {
        ListNode newHead = new ListNode(-1);
        ListNode tmp = newHead;
        while (headA != null && headB != null) {
            if(headA.val <headB.val) {
                tmp.next = headA;
                headA = headA.next;
                tmp = tmp.next;
            } else {
                tmp.next = headB;
                headB = headB.next;
                tmp = tmp.next;
            }
        }
        if (headA != null) {
            tmp.next = headA;
        }
        if (headB != null) {
            tmp.next = headB;
        }
        return newHead.next;
    }
    public ListNode findKthToTail(ListNode head,int k) {
        if (k <= 0 || head == null) {
            return null;
        }
        ListNode fast = head;
        ListNode slow = head;
        while (k - 1 != 0) {
            fast = fast.next;
            if (fast == null) {
                return null;
            }
            k--;
        }
        while (fast.next != null) {
            fast = fast.next;
            slow = slow.next;
        }
        return slow;
    }
    public  ListNode middleNode() {
        if (head == null) {
            return null;
        }
        ListNode fast = head;
        ListNode slow = head;
        while (fast != null && fast.next != null) {
            fast = fast.next.next;
            if (fast == null) {
                return slow;
            }
            slow = slow.next;
        }
        return slow;
    }
    public ListNode reverseList() {
        if (this.head == null) {
            return null;
        }
        ListNode cur = this.head;
        ListNode prev = null;
        while (cur != null) {
            ListNode curNext = cur.next;
            cur.next = prev;
            prev = cur;
            cur = curNext;
        }
        return prev;
    }
    public boolean hasCycle(ListNode head) {
        if (head == null) {
            return false;
        }
        ListNode fast = head;
        ListNode slow = head;
        while (fast != null && fast.next != null) {
            fast = fast.next.next;
            slow = slow.next;
            if (fast == slow) {
                return true;
            }
        }
        return false;
    }
    public ListNode detectCycle(ListNode head) {
        if (head == null) {
            return null;
        }
        ListNode fast = head;
        ListNode slow = head;
        while (fast != null && fast.next != null) {
            fast = fast.next.next;
            slow = slow.next;
            if (fast == slow) {
                break;
            }
        }
        if (fast == null || fast.next == null) {
            return null;
        }
        fast = head;
        while (fast != slow) {
            fast = fast.next;
            slow = slow.next;
        }
        return fast;
    }

}
